1. Field of the Invention
The present invention relates to a balloon catheter. More particularly, the invention relates to a balloon catheter for use in the angiography.
2. Description of the Prior Art
The main object of the angiography in which a contrast medium is injected in a blood vessel and the flow of the injected contrast medium is observed according to the roentgenography is to diagnose not only expansion of the morbid state in the blood vessel per se but also expansion of the morbid state to various organs and surrounding textures by a compressed vessel image and an infiltrated vessel image. Improvements have been perpetually made on this angiography. Among these improvements, development of the Seldinger method is important and significant. More specifically, before development of this method, insertion of catheters into blood vessels had been performed by surgical operations, but following the Seldinger method development, the selective angiography has made a rapid progress because insertion of catheters into blood vessels can be performed percutaneously with ease (without surgical operations) when this method is adopted.
Recently, there has been adopted and practised the selective angiography in which the top end of a catheter inserted in the main artery or main vein is introduced even into a primary or secondary branch of the main artery or main vein and the objective blood vessel is selectively visualized. According to this method, overlap visualization of the objective blood vessel with other blood vessles can be prevented, and the roentgengraphy can be performed with an improved visualizing capacity because dilution of the contrast medium in the blood vessel is prevented. Accordingly, the diagnosis precision is remarkably improved as compared with the conventional method in which a catheter is inserted in the main artery or main vein. As a procedure for practising this selective angiography, there has ordinarily been adopted a method in which a top of the catheter is first bent and then the catheter is inserted into the objective blood vessel while turning, advancing and retreating the catheter under X-ray fluoroscopy.
Indeed, the diagnosis precision is increased in this selective angiography as compared with the conventional angiographical methods. However, even according to this selective angiography, it is impossible to visualize minute blood vessels or insert a catheter beyond crooked and indented blood vessels if conventional catheters are employed. For example, it is impossible to guide a catheter to the intracranial artery. It is considered that this will be possible if a balloon catheter having a fine diameter is employed. There has been the balloon catheters in which a catheter and a balloon are fixed together by a silk yarn or rubber yarn [see, for example, Neuroradiology, 9, 145-156 (1975)], and these conventional catheters involve a risk of separation of the balloon from the catheter when the balloon is inflated in the blood vessel. Moreover, a stepwise change of the thickness of the balloon is caused in an attachment portion where the balloon is attached to the catheter and the resulting step portion hinders insertion or withdrawal of the balloon catheter and there is a risk that the blood vessel will be damaged by this step portion. Furthermore, the catheter of the balloon catheter to be used for the above purpose should have such an appropriate flexibility as will facilitate insertion of the catheter into the blood vessel and movement of the catheter in the blood vessel.